Field of the Invention
This invention relates to development apparatus for use in an electrostatographic copier or printer, and more particularly, to such an apparatus which is precharged or preloaded for clean and safe field installation in such a copier or printer.
As disclosed, for example, in commonly assigned U.S. Pat. No. 4,797,704, the use, in electrostatographic copiers and printers, of development apparatus which have been precharged or preloaded with developer material, is well known. The developer material used in the precharging may be single component consisting only of toner particles, or two-component consisting of carrier particles and toner particles. Where two-component developer material, as such, is used, the development apparatus will include mixing means, in addition to means for moving and applying the mixed developer material to an image to be developed.
Typically, a precharged or preloaded development apparatus includes a replenishment toner particle chamber and a mixing chamber. The mixing chamber is precharged or preloaded with developer material. The mixing chamber also contains the means for moving and applying the developer material, as well as the means, as in the case of two-component developer material for mixing the same. In the latter case, effective mixing can be achieved, on the one hand, only if the quantity of developer material requiring mixing is small enough so as to be directly impacted and moved by the mixing means which can be a small auger or a small ribbon blender.
On the other hand, there is an important need and desire to make such precharged apparatus last a reasonably long time after installation. Typically, in order for such a precharged development apparatus to last a reasonably long time, the mixing chamber, for example, has to be made reasonably big, thereby resulting in a big overall apparatus. Unfortunately, when the apparatus is that big, a small auger or small ribbon blender will occupy only a small portion of its mixing chamber. Therefore, in order not to end up with ineffective mixing as discussed above, the precharged mixing chamber ordinarily will contain only a very small amount of two-component developer material in such a big mixing chamber. Such a small quantity of loose powdery material in such a big chamber undesirably will cause problems.
For example, during the handling of such a precharged or preloaded apparatus prior to its installation in a copier or printer, it is reasonable to expect that the apparatus will be moved and placed in several of various orientations. As a result, the small quantity of developer material therein will undesirably be caused to move about substantially and turbulently within the rest of the mixing chamber. Since such a mixing chamber in a development apparatus has to be open to the outside of the apparatus for image development, such substantial and turbulent movement of the small quantity of preloaded developer material is likely to result (i) in aeration of the toner particles, (ii) in leakage, and (iii) even in undesirable contamination of adjacent components within a host copier or printer.
Where a lid, cover or seal is used in such a development apparatus to close the development opening into the mixing chamber, such substantial and turbulent movement is still likely to soil the lid or cover with developer material in such a manner that removal of the lid or cover by an operator becomes a very messy job. Consequently, there is a need to provide a precharged, that is preloaded, development apparatus which is capable (i) of utilizing two-component developer material, (ii) of lasting a relatively long period of time, and (iii) of clean and contamination-free field installation in a host copier or printer.